Part 42 (1/2)

The oil-tubes are sometimes called the _se-baceous folli-cles_.

[Ill.u.s.tration: 4. A small hair from the scalp, with its oil-glands. The glands (A) form a cl.u.s.ter around the shaft of the hair-tube, (C.) These ducts open into the sheath of the hair, (B.) All the figures, from 1 to 4, are magnified thirty-eight diameters.]

631. What is said of these tubes in the eyelids? In the ear? In the scalp? What are these glands sometimes called?

_Observation._ Among the inhabitants of cities, and especially in persons who have a torpid state of the skin, the contents of the oil-tubes become too dense and dry to escape in the usual manner. Thus it collects, distends the tube, and remains until removed by art. When this impacted matter reaches the surface, dust and smoke mix with it, then it is recognized by small, round, dark spots. These are seen on the forehead, nose, and other parts of the face. When this matter is pressed out, the tube gives it a cylindrical form. The parts around the distended tubes sometimes inflame. This const.i.tutes the disease called, _”acne punc-tata.”_

632. The PERSPIRATORY APPARATUS consists of minute cylindrical tubes, which pa.s.s inward through the cuticle, and terminate in the deeper meshes of the cutis vera. In their course, each little tube forms a beautiful spiral coil; and, on arriving at its destination, coils upon itself in such a way as to const.i.tute an oval-shaped, or globular ball, called the _perspiratory gland_.

633. The opening of the perspiratory tube on the surface of the cuticle, namely, ”the pores,” is also deserving of attention. In consequence of its extremity being a section of a spirally-twisted tube, the aperture is oblique in direction, and possesses all the advantages of a valvular opening, preventing the ingress of foreign injurious substances to the interior of the tube and gland.

634. ”To arrive at something like an estimate of the value of the perspiratory system, in relation to the rest of the organism, I counted the perspiratory pores on the palm of the hand, and found 3528 in a square inch. Now each of these pores being the aperture of a little tube about a quarter of an inch long, it follows, that in a square inch of skin on the palm of the hand there exists a length of tube equal to 882 inches, or 73 feet. Surely such an amount of drainage as seventy-three feet in every square inch of skin--a.s.suming this to be the average for the whole body--is something wonderful and the thought naturally intrudes itself, What if this _drainage_ be obstructed?

What is said of the retention of the unctuous matter in the oil-tubes?

632. Of what does the perspiratory apparatus consist? 633. What is peculiar in the opening of the perspiratory tubes on the surface of the cuticle? 634. How many perspiratory pores did Dr. Wilson count upon a square inch of skin on the palm of the hand?

[Ill.u.s.tration: Fig. 116. A perspiratory gland from the palm of the hand, magnified forty diameters. 1, 1, A twisted tube composing the gland. 2, 2, The two excretory ducts from the gland. These unite to form one spiral tube, that perforates the cuticle, (3,) and opens obliquely on its surface at 4. The gland is imbedded in cells filled with fat, which are seen at 5, 5.]

What does fig. 116 represent?

635. ”Could we need a stronger argument for enforcing the necessity of attention to the skin? On the pulps of the fingers, where the ridges of the sensitive layer of the true skin are somewhat finer than in the palm of the hand, the number of pores on a square inch a little exceeded that of the palm; and on the heels, where the ridges are coa.r.s.er, the number of pores on the square inch was 2268, and the length of the tube 567 inches, 47 feet.

636. ”To obtain an estimate of the length of tube of the perspiratory system of the whole surface of the body, I think that 2800 might be taken as a fair average of the number of pores in the square inch; and consequently, 700, the number of inches in length. _Now, the number of square inches of surface in a man of ordinary height and bulk is 2500; the number of pores, therefore, 7,000,000; and the number of inches of perspiratory tube is 1,750,000; that is, 145,833 feet, or 48,611 yards, or nearly TWENTY-EIGHT miles!_”--_Wilson._

Give other computations in this paragraph. 635. What is said of the number of these pores on the pulp of the fingers? On the heels? 536.

What is an average number of pores and length of tube of the whole surface of the body? Give the summary of the number of pores, and number or inches of perspiratory tube.

CHAPTER x.x.xII.

PHYSIOLOGY OF THE SKIN.

637. The skin invests the whole of the external surface of the body, following all its prominences and curves, and gives protection to all the organs it encloses, while each of its several parts has a distinct use.

638. The cuticle is insensible, and serves as a sheath of protection to the highly sensitive skin (_cutis vera_) situated beneath it. The latter feels; but the former blunts the impression which occasions feeling. In some situations, the cuticle is so dense and thick, as wholly to exclude ordinary impressions. Of this we see an example in the ends of the fingers, where the hard and dense nail is the cuticle modified for the purpose referred to. Were the nervous tissue of the true skin not thus protected, every sensation would be so acute as to be unpleasant, and contact with external bodies would cause pain.